The present invention relates to load bearing fabric, and more particularly to components and methods for securing a load bearing fabric to a support structure.
The use of load bearing fabrics continues to grow dramatically in various industries, including the automotive, office and home seating industries. The term “load bearing fabric” is commonly used to refer to a class of high strength, highly durable textiles that are typically woven from elastomeric monofilaments and conventional yarns. Some of today's load bearing fabrics have greater strength and durability characteristics than spring steel and other conventional load bearing materials. In addition to their strength and durability characteristics, load bearing fabrics are lightweight and typically have a high modulus of elasticity. Therefore, they are well-suited for use in a variety of applications where a strong and durable yet lightweight or elastic load bearing surface is desired, for example, in seating, cots and wheelchair applications. Further, because load bearing fabrics are aesthetically pleasing they can and often are exposed during use, for example, as the seat or back of an office chair. This eliminates the need to cover or trim conventional load bearing surfaces.
One particularly important challenge related to the use of load bearing fabric is the challenge of attaching the fabric to the support structure. Although load bearing fabrics have high strength and durability characteristics, they must be properly attached to the support structure to provide an end product with the desired strength and durability. This task is particularly challenging because it is typically important to attach the fabric to the support structure in a stretched or tensioned state. This applies a constant load to the connection between the fabric and the support structure.
Conventional attachment methods often fail to provide the necessary strength and durability to withstand the forces applied to the fabric. As a result, the fabric separates from the support structure under conditions that the fabric is otherwise well-suited to survive. In some applications, the bond itself may fail and in other applications, the method of attachment may cause the fabric to unravel or separate along the periphery of the fabric. Accordingly, there is an ongoing effort to develop new and improved methods and components for securing the load bearing fabric to the support structure.
Perhaps the most common use of load bearing fabric is in the furniture industry, where load bearing fabrics are used to form the seat and back of task seating, executive chairs and other office chairs. In the furniture industry, load bearing fabrics are typically secured to a support structure by an outer ring, often in the form of a peripheral frame. The fabric is first attached to the outer ring and then the outer ring is attached to the support structure, such as the seat frame or back frame. In such applications, the challenge is to secure the outer ring in a way that provides a strong and durable bond without damaging or promoting unraveling of the fabric. One conventional method for addressing these issues is to secure the load bearing fabric to an outer ring through encapsulation. In general, encapsulation involves the molding of an outer ring in situ about the peripheral edge of the fabric. During the molding process, the material of the outer ring flows through and becomes intimately intersecured with the fabric. The outer ring is then secured to the support structure using fasteners or other conventional techniques and apparatus.
Although encapsulation provides a strong and durable bond, it suffers from a number of disadvantages. To provide the chair with a firm seat and back, the fabric must typically be tightly stretched over the chair and back frames. The conventional method for providing the fabric with the desired amount of stretch is to hold the fabric in a stretched position while the outer ring is molded in place about the fabric. This operation involves the use of expensive looms and stretching machinery. The stretching machinery stretches the fabric to the desired position. The stretched fabric is then mounted to the loom, which holds the fabric in the stretched position during the molding process. It may also be necessary to provide molding equipment that is specially configured to operate while the loom holds the stretched fabric. Further, when the molded outer ring and fabric emerge from the mold, the force of the stretched fabric can cause the outer ring to deform, for example, to bow or “potato chip.” This creates the need to return the outer ring to the desired shape, typically using additional machinery, prior to attachment to the support structure. As can be seen, this conventional encapsulation method requires a relatively complex manufacturing process that employs expensive looms and stretching machinery.
Another alternative is to mold the outer ring from an elastic or stretchable material so that the outer ring can be stretched after it is intersecured with the fabric. In general, this process involves molding the outer ring about the load bearing fabric while the load bearing fabric is in a relaxed state. After the molding process, the outer ring is stretched or expanded to apply the desired tension to the fabric. Although this process provides a marked improvement over the prior art, it requires a separate stretching or expansion step following the molding process.